RFR [JDK8]: 7169894: JAXP Plugability Layer: using service loader

[Paul Sandoz]

Hi Joe,

On Aug 30, 2012, at 1:08 AM, Joe Wang <huizhe.wang at oracle.com> wrote:

> I actually updated the webrev yesterday with your suggestion.  
> 

OK! Sorry if i am being stubbornly persistent!


> Recall our discussions back in June, the suggestion was to delegate to the ServiceLoader, e.g. ServiceLoader.load(serviceClass). The rational was that the ServiceLoader uses context and then bootstrap class loader.
> 

Yes.


> The spec for public static <S> ServiceLoader<S> load(Class<S> service, ClassLoader loader) states:
> loader - The class loader to be used to load provider-configuration files and provider classes, or null if the system class loader (or, failing that, the bootstrap class loader) is to be used
> 
> This is different. In JAXP, null is recognized as bootstrap classloader, but the  ServiceLoader actually assumes it as system class loader.  This will be a problem, whether or now a classloader is passed to the load method.
> 

It's slightly different. For loading the provider-configuration file SL does:

                    if (loader == null)
                        configs = ClassLoader.getSystemResources(fullName);
                    else
                        configs = loader.getResources(fullName);

For loading the class:

                S p = service.cast(Class.forName(cn, true, loader)
                                   .newInstance());

And the JavaDoc for Class.forName states:

    "If the parameter loader is null, the class is loaded through the bootstrap class loader."

So there is some vagueness in the JavaDoc of SL of when the system CL is utilised.

However, i think things are consistent with loading the provider-configuration file, it's a bit of a tangle but AFAICT previously loading the configuration file deferred to SecuritySupport.getResourceAsStream which does:

                   if (cl == null) {
                        ris = Object.class.getResourceAsStream(name);
                    } else {
                        ris = cl.getResourceAsStream(name);
                    }

And the JavaDoc of Class.getResourceAsStream states:

  "If this object was loaded by the bootstrap class loader, the method delegates to 
   ClassLoader.getSystemResourceAsStream(java.lang.String)"

Paul.